Effect of Targeting Left Ventricular Lead Position on the Rate of Response to Cardiac Resynchronization Therapy.

Background. Identifying & optimizing strategies to reduce the burden of heart failure (HF) is vital. Despite advances in pharmacotherapy, patients with HF are at high risk for death & hospitalization. Over 25% of patients with systolic HF have dyssynchronous ventricular contraction that results in paradoxical septal motion, further impairing left ventricular (LV) function & HF progression. Cardiac resynchronization therapy (CRT) synchronizes ventricular mechanical activity, improves cardiac output & reduces HF symptoms. However, ~50% of patients do not clearly respond to CRT. Sub-optimal placement of the LV pacing lead appears to be an important reason for non-response.

Screening. Mechanical synchrony is vitally important in optimizing CRT response. Patients will be pre-screened with echocardiograms (echo) & CRT provided to only those with dyssynchrony. The predicted rate of CRT response in patients pre-screened for dyssynchrony is estimated at 65%.

CRT response. The combined use of a valid & simple measure of functional capacity with a reproducible measure of LV volume is optimal in identifying CRT responders. These outcomes will be assessed using the Specific Activity Scale & radionuclide angiography (RNA), respectively.

Primary hypothesis. Targeted LV lead placement will result in an increased probability of CRT response at 52 weeks vs. usual (lateral wall) lead placement. CRT response will be defined as ≥ 10% relative reduction in LV end systolic volume & ≥ 1 Specific Activity Scale class improvement.

Inclusion criteria

• LV EF ≤ 0.40 measured within 3 months of enrollment,
• SAS class 3 or 4 symptoms indicative of moderate to severe functional capacity limitation due to heart failure within 1 month of enrollment.
• Confirmed dyssynchrony on screening echo (1.1.9), &
• On stable doses of ACE inhibitor or angiotensin II blocker & a beta-blocker for ≥ 2 months unless medically contra-indicated.
• Controlled heart rate if in permanent AF (resting <70 & maximal <120).

Exclusion criteria

• Unable or unwilling to provide informed consent,
• Medical condition other than heart failure likely to cause death < 1 year,
• Cardiac transplant planned within 6 months,
• Known contra-indication to transvenous CRT device implant (e.g., active sepsis, artificial tricuspid valve, known vascular occlusion that will prevent delivery of leads transvenously),
• Clinically significant myocardial infarction within last 2 months, or
• Coronary bypass graft surgery ≤ 2 months or coronary angioplasty ≤ 1 month